1. Field of the Invention
The present invention relates to an internal power supply voltage generating circuit of semiconductor memory devices. More specifically, the present invention relates to an internal power supply voltage generating circuit with reduced standby current of a Pseudo Static Random Access Memory (PSRAM).
2. Discussion of Related Art
Generally, the standby current of a PSRAM consists of the consumption current of internal circuits of semiconductor memory devices, the refresh current, and the leakage current. In the prior art, the ratio of the leakage current to the standby current is very small. As transistors and various elements gradually become very small, the ratio of the leakage current to the standby current becomes very large and cannot be ignored. This leakage current is mostly a channel leakage current of the transistor and is proportional to the width of the transistor. As mobile devices become popular, the need for low-power and high-density memory becomes important. Thus, an increase of the leakage current becomes a significant problem.
FIG. 1 is a block diagram of an internal power supply voltage generating circuit and internal circuits using an internal power supply voltage.
Referring to FIG. 1, the internal power supply voltage generating circuit 10 includes a plurality of internal power drivers 10-1 to 10-n. Each of the internal power drivers 10-1 to 10-n generates an external power supply voltage (Vext) and an internal power supply voltage (Vint). The generated internal power supply voltage (Vint) is used to drive internal circuits of semiconductor memory devices such as a high voltage (VPP) generator 20, a cell power supply voltage (Vcore) generator 30 and a peripheral circuit 40.
Each of the internal power drivers 10-1 to 10-n is under the control of a deep power-down detection signal (PWb). The deep power-down detection signal (PWb) becomes a logical high in deep power-down mode to turn off the PMOS transistors of the internal power drivers 10-1 to 10-n, and becomes a logical low in modes other than the deep power-down mode to turn on the PMOS transistors of the internal power drivers 10-1 to 10-n. If the PMOS transistors of the internal power drivers 10-1 to 10-n are turned on, the current flows and the internal power supply voltage (Vint) is generated.
The internal power supply voltage drivers 10-1 to 10-n generate the current in order to generate the internal power supply voltage (Vint) in standby mode. However, the current generated in the internal power drivers 10-1 to 10-n become the origin of the leakage current in standby mode.
One method of reducing the leakage current is to reduce the width of the PMOS transistors of the internal power drivers 10-1 to 10-n. It is, however, impossible to reduce the width of the internal power drivers 10-1 to 10-n constantly. This is because the current (i.e., the internal power supply voltage) necessary for the operation (driving) of the internal circuits must be supplied in a mode other than the standby mode or the deep power-down mode.